A histological study on gonadal development of black amur bream (Megalobrama terminalis)

We used histological methods to observe the gonadal development of Megalobrama terminalis, and decribed the morphology in each type of germ cell and structural feature in ovary and testis. The results indicate that M. terminalis is a one-time spawning type fish, whose ovary development type is partially synchronous. The ovary was thin or flat. The ovarian development had oogonia, monolayer follicular phase, yolk vesicle phase, yolk filling phase, maturation phase and degeneration phase. Occurrence of oocytes had undergone three stages: oogonia, primary oocytes and secondary oocytes. The nucleolar efflux phenomenon occurred in the primary oocytes of ovary from the late Stage II to the early Stage III. The testis was thin or straight with a leaflet structure. The spermatogenesis had undergone five stages: spermatogonia, primary spermatocyte, secondary spermatocyte, spermatid and sperm. The spermatids were filled with spermatozoa and the spermatic capsules disappearred in breeding season.